MAC-in-MAC standard defined in 802.1ah is adopted in a Provider Backbone Bridge (PBB) network. The basic idea of MAC-in-MAC is: encapsulating 802.1 ah header with a user Ethernet packet to form a backbone frame. In the PBB network, backbone frame is forwarded according to Backbone Source MAC address (B-SA) and Backbone Destination MAC address (B-DA) of B-MAC in the 802.1ah header.